U.S. patent number 4,756,959 [Application Number 07/016,288] was granted by the patent office on 1988-07-12 for sheet for use in firing base plates.
This patent grant is currently assigned to Daito Kako Kabushiki Kaisha, Ishizuka Garasu Kabushiki Kaisha, Kabushiki Kaisha Hayashi Takatoshi Shyoten, Nagara Seishi Kabushiki Kaisha. Invention is credited to Fukashi Hashimoto, Yoshio Hayashi, Riichiro Ieda, Toshikuni Ito, Koichi Morimoto.
United States Patent |
4,756,959 |
Ito , et al. |
July 12, 1988 |
Sheet for use in firing base plates
Abstract
The present invention relates to a sheet which may be used in
firing ceramic faced base plates, glass faced base plates and metal
faced base plates. The sheet comprises a combustible sheet such as
a pulp paper and a coating layer coated on at least one surface of
the combustible sheet. The coating layer comprises a powder of a
material with a high melting point and a powder of carbon which may
be formed separately from the layer comprising the powder of a
material having a high melting point. The coating layer comprising
the powder of carbon effectively prevents shrinkage of the sheet
during firing, and thus prevents adhesion between adjacent stacked
base plates and between the base plates and the supporting base.
The sheet of the present invention further provides a layer of a
uniform breadth which prevents the formation of undulations and
pin-holes in the base plates during firing.
Inventors: |
Ito; Toshikuni (Aichi,
JP), Morimoto; Koichi (Iwakura, JP),
Hashimoto; Fukashi (Gifu, JP), Hayashi; Yoshio
(Gifu, JP), Ieda; Riichiro (Gifu, JP) |
Assignee: |
Ishizuka Garasu Kabushiki
Kaisha (Nagoya, JP)
Daito Kako Kabushiki Kaisha (Gifu, JP)
Nagara Seishi Kabushiki Kaisha (Motosu, JP)
Kabushiki Kaisha Hayashi Takatoshi Shyoten (Gifu,
JP)
|
Family
ID: |
27288992 |
Appl.
No.: |
07/016,288 |
Filed: |
February 19, 1987 |
Foreign Application Priority Data
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Feb 20, 1986 [JP] |
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61-36147 |
Aug 19, 1986 [JP] |
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61-193829 |
Sep 20, 1986 [JP] |
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61-222932 |
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Current U.S.
Class: |
428/323; 264/608;
264/672; 428/325; 428/328; 428/329; 428/414; 428/515; 428/537.5;
432/241; 432/258 |
Current CPC
Class: |
C04B
35/64 (20130101); F27D 1/0006 (20130101); F27D
5/00 (20130101); F27D 5/0018 (20130101); Y10T
428/31909 (20150401); Y10T 428/31515 (20150401); Y10T
428/31993 (20150401); Y10T 428/257 (20150115); Y10T
428/25 (20150115); Y10T 428/256 (20150115); Y10T
428/252 (20150115) |
Current International
Class: |
C04B
35/64 (20060101); F27D 1/00 (20060101); F27D
5/00 (20060101); B32B 018/00 (); B32B 005/16 ();
F27D 003/12 (); F27D 005/00 () |
Field of
Search: |
;428/323,325,328,329,331,408,414,515,537.5 ;432/6,258,259
;264/58 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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236006 |
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Sep 1987 |
|
EP |
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3534886 |
|
Apr 1986 |
|
DE |
|
58-99163 |
|
Jun 1983 |
|
JP |
|
182727 |
|
Aug 1985 |
|
JP |
|
60-8991 |
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Aug 1985 |
|
JP |
|
61-56188 |
|
Mar 1986 |
|
JP |
|
49188 |
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Mar 1987 |
|
JP |
|
Primary Examiner: Kittle; John E.
Assistant Examiner: Rucker; Susan S.
Attorney, Agent or Firm: Cushman, Darby & Cushman
Claims
What is claimed is:
1. A sheet suitable for use in firing ceramic faced base plates,
said sheet being placed between said ceramic faced base plates
during firing, said sheet comprising:
a combustible sheet; and
a coating layer coated on at least one surface of said combustible
sheet, said coating layer comprising (a) 25% to 90% by weight of a
powder of ceramics having a high melting point selected from the
group consisting of Al.sub.2 O.sub.3 and ZrO.sub.2 and (b) 5% to
70% by weight of a powder of carbon.
2. The sheet according to claim 1 wherein said combustible sheet
comprises a pulp paper.
3. The sheet according to claim 1 wherein said combustible sheet
comprises a sheet of combustible plastic consisting of polyvinyl
alcohol.
4. The sheet according to claim 1 wherein said powder of ceramics
and said powder of carbon are mixed with an organic binder.
5. The sheet according to claim 4 wherein said organic binder is
included in an amount of 5% to 30% by weight in said coating
layer.
6. The sheet according to claim 4 wherein said organic binder
comprises an acrylic resin binder.
7. The sheet according to claim 1 wherein said coating layer is
coated on each surface of said combustible sheet.
8. A sheet suitable for use in firing base plates constructed by
pressing a powder of one of ceramics, glass, and metal into the
form of a plate, said sheet being placed between said base plates
during firing, said sheet comprising:
a combustible sheet; and
a coating layer coated on at least one surface of said combustible
sheet, said coating layer comprising (a) 25% to 90% by weight of a
powder of at least one kind of ceramics selected from the group
consisting of nitride, carbonide, and ferrite and (b) 5% to 90% by
weight of a powder of carbon.
9. The sheet according to claim 8 wherein said nitride is selected
from the group consisting of BN, AlN, and Si.sub.3 N.sub.4.
10. The sheet according to claim 8 wherein said carbonide comprises
SiC.
11. The sheet according to claim 8 wherein said ferrite is selected
from the group consisting of Mn-Zn type ferrite and Ni-Zn type
ferrite.
12. The sheet according to claim 8 wherein said combustible sheet
comprises a pulp paper.
13. The sheet according to claim 8 wherein said combustible sheet
comprises a sheet of combustible plastic consisting of polyvinyl
alcohol.
14. The sheet according to claim 8 wherein said powder of ceramics
and said powder of carbon are mixed with an organic binder.
15. The sheet according to claim 14 wherein said organic binder is
included in an amount of 3% to 30% by weight in said coating
layer.
16. The sheet according to claim 14 wherein said organic binder
comprises acrylic resin.
17. The sheet according to claim 8 wherein said coating layer is
coated on each surface of said combustible sheet.
18. A sheet suitable for use in firing ceramic faced base plates,
said sheet being placed between said ceramic faced base plates
during firing, said sheet comprising:
a combustible sheet;
first coating layers comprising a powder of carbon coated on both
surfaces of said combustible sheet; and
a second coating layer comprising a powder of material with a high
melting point coated on a surface of at least one of said first
coating layers.
19. The sheet according to claim 18 wherein said combustible sheet
comprises a pulp paper.
20. The sheet according to claim 18 wherein said combustible sheet
comprises a sheet of combustible plastic consisting of polyvinyl
alcohol.
21. The sheet according to claim 18 wherein said first coating
layers consist of the powder of carbon and a binder.
22. The sheet according to claim 18 wherein the breadth of each of
said first coating layers is 15-50 microns.
23. The sheet according to claim 18 wherein said second coating
layer is adhered via an adhesive layer of resin selected from the
group consisting of acrylic resin and epoxy resin to a surface of
at least one of said first coating layers.
24. The sheet according to claim 18 wherein said material with a
high melting point is a ceramics selected from the group of
alumina, zirconia, silicon carbide, silicon nitride, aluminum
nitride and boron nitride.
25. The sheet according to claim 18 wherein said material with a
high melting point is a ferrite selected from the group of
manganese-zinc and nickel-zinc.
26. A sheet suitable for use in firing ceramic faced base plates,
said sheet being placed between said ceramic faced base plates
during firing, said sheet comprising:
a combustible sheet;
a coating layer coated on at least one surface of said combustible
sheet, said coating layer comprising (a) a powder of a material
with a high melting point in an amount of 0.5% to 25% by weight,
(b) a powder of carbon in an amount of 5% to 90% by weight, (c) a
dispersing agent in an amount of 0.1to 8% by weight, and (d) a
binder occupying a remaining portion.
27. The sheet according to claim 26 wherein said dispersing agent
is a surface-active agent.
28. The sheet according to claim 26 wherein said binder ia a
synthetic resin binder.
29. The sheet according to claim 26 wherein said combustible sheet
comprises a pulp paper.
30. The sheet according to claim 26 wherein said combustible sheet
comprises a sheet of combustible plastic consisting of polyvinyl
alcohol.
31. The sheet according to claim 26 wherein said coating layer is
coated on said combustible sheet by means of one of flow dipping
coating, electrostatic coating and dipping coating and then
dried.
32. The sheet according to claim 26 wherein said material with a
high melting point is a ceramics with a high melting point selected
from the group of alumina, zirconia, silicon carbide, silicon
nitride, aluminum nitride and boron nitride and the average
particle size of said powder of a material with a high melting
point is 30-40 microns.
33. The sheet according to claim 26 wherein said material with a
high melting point is a ferrite selected from the group consisting
of manganese-zinc and nickel-zinc.
34. The sheet according to claim 27 wherein said surface-active
agent is an agent selected from the group consisting of a fluoric
agent, a nonionic agent and an anionic agent.
35. The sheet according to claim 26 wherein said binder comprises
plastics selected from the group consisting of acrylic resin and
epoxy resin.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sheet which may be used in
firing ceramic faced base plates, metal faced base plates and glass
faced base plates. More specifically, the present invention relates
to a sheet which may be placed between adjacent stacked base plates
and between the base plates and the supporting base during firing
to prevent adhesion. The sheet additionally prevents the formation
of undulations and pin-holes in the base plates during firing.
2. Description of the Prior Art
When ceramic faced base plates are fired according to the
conventional method, a powder of material with a high melting
point, such as Al.sub.2 O.sub.3 is scattered on the ceramic faced
base plates by hand, following which ceramic faced base plates are
stacked in a vertical direction and fired. However, due to the
uneven scattering effect obtained by this method, undulations and
pin-holes form in the ceramic faced base plates during firing. In
addition, inferior products are often produced due to the adhesion
of Al.sub.2 O.sub.3 powder to undesirable portions of the ceramic
faced base plates. Furthermore, the method of scattering the powder
on the base plates by hand increases the cost of production.
Japanese Patent Publication SHO No. 60-8991 proposes a sheet which
comprises a powder of Al.sub.2 O.sub.3 or ZrO.sub.2 scattered
within a paper or plastic sheet to overcome the above-described
drawbacks in the method of scattering a the powder with a high
melting point on the base plates by hand. However, such a sheet
shrinks considerably during firing according to the type of the
sheet used. As a result, the peripheral portions of the ceramic
faced base plates often adhere to each other during and following
firing. To prevent such adhesion, the sheet thus comprising the
powder must be increased in size by the estimated amount of
shrinkage expected during firing and this estimation is very
difficult.
During firing, the stacked ceramic faced base plates are usually
placed on a supporting base. Metal-faced base plates, which are
constructed by pressing a powder of a metal such as cemented
carbide into the form of a plate, may also be stacked and fired.
During firing, the stacked metal-faced base plates are usually put
on a supporting base, as in the case of the ceramic faced base
plate. Since ceramics-faced base plates and metal-faced base plates
shrink during firing, the bottom surface of the stacked base plates
becomes scratched due to abrasion with the surface of the
supporting base, thereby producing an inferior product. Even in the
case of placing the sheet comprising a powder scattered within a
paper, as disclosed by Japanses Patent Publication SHO No. 60-8991,
between the stacked ceramic faced or metal faced base plates and
the supporting base, the lubricating effect of said sheet is
insufficient to prevent abrasion. In particular, almost no
lubricating effect may be expected in the case of metal-faced base
plates.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to provide a sheet
which may be used in firing ceramic faaced base plates, glass faced
base plates and metal faced base plates, which sheet is not likely
to shrink during firing.
It is another object of the present invention to provide a sheet
which may be used in firing ceramic faced base plates, glass faced
base plates and metal faced base plates, which sheet prevents
adhesion between adjacent stacked base plates and between the base
plates and the supporting base.
It is a further object of the present invention to provide a sheet
which may be used to prevent formation of undulations and pin-holes
in ceramic faced base plates, glass faced base plates and
metal-faced base plates during firing.
The sheet of the present invention may be of the following
structures.
(1) The sheet of the present invention which may be used to fire
ceramic faced base plates may comprise (1) a combustible sheet, and
(2) a coating layer coated on at least one surface of the
combustible sheet, the coating layer comprising (a) a powder of
ceramics with a high melting point selected from the group
consisting of Al.sub.2 O.sub.3 and ZrO.sub.2 and (b) a powder of
carbon. This sheet corresponds to a first embodiment of the present
invention.
(2) The sheet of the present invention which may be used to fire
ceramic faced base plates, glass faced base plates and metal faced
base plates may comprise (1) a combustible sheet, and (2) a coating
layer coated on at least one surface of the combustible sheet, the
coating layer comprising (a) a powder of at least one kind of
ceramics selected from the group consisting of a nitride, a
carbonide (carbide), and a ferrite and (b) a powder of carbon. This
sheet corresponds to a second embodiment of the present
invention.
(3) The sheet of the present invention which may be used to fire
ceramic faced base plates may comprise (1) a combustible sheet, and
(2) first coating layers coated on both surfaces of the combustible
sheet and a second coating layer comprising a powder of a material
having a high melting point coated on a surface of at least one of
the first coating layers. This sheet corresponds to a third
embodiment of the present invention.
(4) The sheet of the present invention which may be used to fire
ceramic faced base plates may alternatively comprises (1) a
combustible sheet, and (2) a coating layer coated on at least one
surface of the combustible sheet, the coating layer comprising (a)
a powder of a material having a high melting point in an amount of
0.5% to 25% by weight, (b) a powder of carbon in an amount of 5% to
90% by weight, (c) a dispersing agent in an amount of 0.1 to 8% by
weight, and (d) a binder forming the remainder of the coating
layer.
Because the coating layer which includes the powder of carbon is
coated on the surface of the combustible sheet according to the
method of the present invention, the remaining between the stacked
ceramic faced base plates, glass faced base plates or metal faced
base plates following incineration of the combustible sheet, has a
uniform breadth. Accordingly, undulations and pin-holes are
prevented from forming in said base plates during firing.
Furthermore, since the powder of carbon included in the coating
layer prevents shrinkage of the sheets, adhesion between the
peripheral portions of the ceramic faced base plates, glass faced
base plates or metal faced base plates and between the base plates
and the supporting base are prevented.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other objects and advantages of the present invention
will become apparent from the following detailed description of the
presently preferred exemplary embodiments of the invention taken in
conjunction with the accompanying drawings, wherein:
FIG. 1 is a sectional view of a sheet which may be used in firing
ceramic faced base plates according to the first embodiment of the
present invention;
FIG. 2 is sectional view of a sheet which may be used in firing
ceramic faced base plates, metal faced base plates and glass faced
base plates according to the second embodiment of the present
invention;
FIG. 3 is a sectional view of a sheet which may be used in firing
ceramic faced base plates according to the third embodiment of the
present invention;
FIG. 4 is a sectional view of the sheet of FIG. 3 in the first
stage of construction of the sheet;
FIG. 5 is a sectional view of the sheet of FIG. 3 in the second
stage of construction of the sheet; and
FIG. 6 is a sectional view of a sheet which may be used in firing
ceramic faced base plates according to the fourth embodiment of the
present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A. FIRST EMBODIMENT
Referring now to the drawings, there is illustrated in FIG. 1, a
sheet 1 which may be used in firing ceramic faced base plates 2
according to a first embodiment of the prevent invention. The sheet
1 is placed between the ceramic faced base plates 2 during firing.
The sheet 1 comprises a combustible sheet 3 and a coating layer 4
which is coated on at least one surface of the combustible sheet 3.
The coating layer 4 includes a powder of ceramics 5 with a high
melting point which is selected from the group consisting of and
Al.sub.2 O.sub.3 ZrO.sub.2 and a powder of carbon 6.
The combustible sheet 3 is preferably composed of a pulp paper
which may be entirely incinerated when the ceramic faced base
plates 2 are fired. The combustible sheet 3 may be composed of a
sheet of combustible plastics, such as polyvinyl alcohol. The
powder of ceramics 5 with a high melting point, such as a powder of
Al.sub.2 O.sub.3 and ZrO.sub.2 and the powder of carbon 6 are mixed
together with an organic binder. The mixture is then coated on the
surface of the combustible sheet 3. The coating layer 4 is
preferably coated on both surfaces of the combustible sheet 3 as
shown in FIG. 1. Alternatively, the coating layer 4 may be coated
on one surface of the combustible sheet 3. The coating layer 4
preferably comprises 25% to 90% by weight of the powder of ceramics
5 and 5% to 70% by weight of the powder of carbon 6 which are mixed
with 5% to 30% by weight of an organic binder. The powder of
ceramics 5 functions to prevent the ceramic faced base plates 2
from adhering to each other during firing. If the coating layer 4
comprises the powder of ceramics 5 in an amount less than 25% by
weight, the adhesion-preventing effect of the powder of ceramics is
no longer satisfactory. If the coating layer 4 comprises the powder
of ceramics 5 in an amount greater than 90% by weight, an even
surface of the coating layer 4 is difficult to obtain and the ratio
of the powder of carbon 6 to the powder of ceramics 5 included in
coating layer 4 decreases, which results in decreasing the effects
of the powder of carbon 6 described below.
The powder of carbon 6 functions to inhibit shrinkage of the entire
sheet 1 during firing to such an extent that the shrinkage rate of
the sheet 1 is substantially the same as that of alumina-faced base
plates, which are a typical example of ceramic faced base plates 2.
If the coating layer 4 comprises the powder of carbon 6 in an
amount less than 5% by weight, the shrinkage-inhibiting effect of
the powder of carbon 6 is no larger satisfactory. If the coating
layer 4 comprises the powder of carbon 6 in an amount greater than
70% by weight, it is difficult to coat the coating layer 4 on at
least are surface of the combustible sheet 3.
As the organic binder, an acrylic resin binder may be used. Any
kind of organic binder may be used that does not have an
undesirable effect on the ceramic faced plates 2 during firing.
The sheet 1 thus constructed is placed between the ceramic faced
base plates 2 which are stacked in a vertical direction during the
firing of the ceramic faced base plates 2. The combustible sheet 3
will be incinerated during the diring due to the high temperatures,
leaving the powder of ceramics 5 with a high melting point
remaining between the ceramic faced base plates 2. This powder of
ceramics 5 functions to prevent adhesion between the ceramic faced
base plates 2, obtaining improved results over the powder of
ceramics of the prior art which is scattered by hand on the ceramic
faced base plates prior to firing.
The sheet 1 of the present invention has additional advantages.
Because the sheet 1 of the first embodiment of the present
invention is constructed by coating the coating layer 4 on at least
one surfaces of the combustible sheet 3, a constant breadth of the
coating layer 4 may be easily obtained and the construction of the
sheet 1 is very easy, which results in a decrease in costs. Since
the coating layer 4 comprises the powder of carbon 6 in an amount
of 5% to 70% by weight, the sheet 1 shrinks only to substantially
the same extent as the ceramic faced base plates 2. As a result,
the adhesion between the peripheral portions of the ceramic faced
base plates 2 firing of ceramic faced base plates is effectively
prevented. Furthermore, the surface of the sheet 1 which may be
used in firing ceramic faced base plates according to the present
invention is flat; the construction of an uneven surface and the
formation of pin-holes in the ceramic faced base plates 2 during
firing are effectively prevented.
An example of the first embodiment of the present invention is
described below.
A powder of ceramics 5 of Al.sub.2 O.sub.3 having a grain size of
10-50 microns and in an amount of 55% by weight a powder of carbon
6 having about the same grain size in an amount of 35% by weight
were mixed together with an organic binder of acrylic resin in an
amount of 10% by weight. The mixture was then coated on both
surfaces of a combustible sheet 3 composed of 100% pulp paper
having a width of about 1 mm and then dried to form the coating
layers 4. The sheet thus constructed was cut to a square sheet
having dimensions of 128 mm by 128 mm to form a sheet 1 which may
be used in firing ceramic faced base plates according to the
present invention. Eight ceramic faced based plates 2, each having
dimensions of 128 mm by 128 mm and a width of 1.2 mm, were stacked
in a vertical direction with sheets 1 separating adjacent ceramic
faced base plates 2. The ceramic faced base plates 2 were then
fired. Undulation in ceramic faced base plates 2 thus fired were
measured and compared with those of ceramic faced base plates of
the same material and the same dimensions which were fired with a
ceramics powder scattered by hand on the ceramic faced base plates,
according to the method of the prior art. TABLE 1 below shows the
results of the measurements of undulations taken at the span of 80
mm.
TABLE 1 ______________________________________ Undulations of
Ceramic Faced Base Plates First Embodiment of the Present Invention
Prior Art ______________________________________ Maximum 30.6
microns 59.7 microns Minimum 5.9 microns 31.3 microns R 24.7
microns 28.4 microns -x 20.2 microns 47.0 microns .sigma.n-1 7.6
microns 9.5 microns ______________________________________
As may be seen from TABLE 1, the fired ceramic faced base plates 2
of the first embodiment of the present invention show a superior
eveness of surface over that obtained by the prior art.
In summary, the first embodiment of the present invention provides
a number of advantages, including the following. First, due to the
shrinkage-inhibiting effect of the powder of carbon 6, adhesion
between the peripheral portions of the ceramic faced base plates 2
which takes place in conventional firing of ceramic faced base
plates is prevented. Second, due to the constant breadth of the
layer of the powder of ceramics 5 remaining between the ceramic
faced base plates 2, undulations and pin-holes in the ceramic faced
base plates 2, formed during firing, are effectively prevented.
Third, due to the construction of the sheet 1 wherein the coating
layer 4 of a constant breadth is coated on the combustible sheet 3,
the construction of the sheet 1 which may be used in firing
ceramics faced base plates according to the present invention is
easy, resulting in a decrease in costs.
B. SECOND EMBODIMENT
FIG. 2 illustrates a sheet 11 which may be used in firing base
plates according to a second embodiment of the present invention.
According to the second embodiment, a base plate 12 may be
constructed by pressing a powder of ceramics, a powder of metal,
such as cemented carbide, or a powder of glass into the form of a
plate. The sheet 11 is placed between the stacked base plates 12
during firing. The sheet 11 comprises a combustible sheet 13 and a
coating layer 14 which is coated on at least one surface of the
combustible sheet 13. The coating layer 14 comprises a powder of at
least one type of ceramics 15 selected from the group consisting of
nitride, carbonide and ferrite and a powder of carbon 16.
The combustible sheet 13 is preferably constructed of a pulp paper
which may be entirely incinerated when the plates 12 are fired. The
combustible sheet 13 may be composed of a sheet of combustible
plastics, such as polyvinyl alcohol. A powder of ceramics 15 and a
powder of carbon 16 which have been mixed together with an organic
binder are coated on one or both surfaces of the combustible sheet
13. The powder of ceramics 15 which is included in the coating
layer 14 comprises a nitride, such as BN, AlN, or Si.sub.3 N.sub.4,
a carbonide such as SiC, a ferrite such as Mn-Zn, Ni-Zn or an
arbitrary combination thereof. Generally speaking, the heat
durability characteristics of a carbonide are superior to those of
a nitride which are superior to those of an oxide. These ceramics
have better heat durability characteristics than those of Al.sub.2
O.sub.3. In particular, BN may be used as a mould release agent for
glass. BN also has excellent lubricating characteristics with
respect to glass. Thus, BN is preferably used as the powder of
ceramics included in the sheet 11 which may be used in firing such
base plates that are constructed by pressing a powder of glass into
the form of a plate.
The coating layer 14 preferably comprises a powder of ceramics 15
in an amount of 25% to 95% by weight and a powder of carbon 16 in
an amount of 3% to 70% by weight which are mixed with an organic
binder in an amount of 3% to 30% by weight. The powder of ceramics
15 functions to prevent the base plates 12 from adhering to each
other during firing, as well as functioning to provide lubrication
between the base plates 12. If the coating layer 4 comprises the
powder of ceramics 15 in an amount less than 25% by weight, the
adhesion preventing and lubricating effects of the powder of
ceramics 15 are no layer satisfactory. If the coating layer 14
comprises the powder of ceramics 15 in an amount greater than 95%
by weight, an even surface of the coating layer 14 is difficult to
obtain and, in addition, the ratio of the powder of carbon 16 to
the powder of ceramics 15 included in the coating layer 14
decreases, which results in decreasing the effects of the powder of
carbon 16 described below. The powder of ceramics 15 may be a
powder of an oxide, such as Al.sub.2 O.sub.3 or ZrO.sub.2.
The powder of carbon 16 functions to prevent shrinkage of the
entire sheet 11 during firing to such an extent that the shrinkage
rate of the sheet 11 is substantially the same as that of alumina
base plates, which are a typical example of ceramics base plates 2.
The powder of carbon 16 further functions to provide lubrication
between the base plates 12. If the coating layer 14 comprises the
powder of carbon 16 in an amount less than 3% by weight, the
shrinkage inhibiting effect of the powder of carbon 16 is no larger
satisfactory. If the coating layer 14 comprises the powder of
carbon 16 in an amount greater than 70% by weight, it becomes
difficult to coat the coating layer on at least one surface of the
combustible sheet 13.
As the organic binder, an acrylic resin binder may be used. Any
organic binder may be used that does not have an undesirable effect
on the base plates 12 during firing.
The base plates 12 are constructed by pressing a powder of
ceramics, a powder of glass, or a powder of metal such as cemented
carbide into the form of a plate. The sheet 11 is placed between
adjacent base plates 12 which are stacked in a vertical direction
or between the base plate 12 and the supporting base that supports
the stacked base plates 12. The combustible sheet 13 will be
incinerated during the firing of the base plates due to the high
temperatures, leaving the powder of ceramics 15 with a high melting
point and the powder of carbon 16 between the base plates 12 and
between the base plates 12 and the supporting base. These remaining
powders of ceramics and carbon function to prevent adhesion between
the base plates 12 and between the stacked base plates 12 and the
supporting base, and furthermore, provide lubrication between them
to prevent abrasion between them.
The sheet 11 of the present invention has additional advantages.
Because the sheet 11 of the second embodiment of the present
invention is constructed by coating the coating layer 14 on at
least one surface of the combustible sheet 13, a constant breadth
of the coating layer 14 may be easily obtained and the construction
of the sheet 11 is very easy, which results in a decrease in costs.
Since the coating layer 14 comprises the powder of carbon 16 in an
amount of 3% to 70% by weight, the sheet 11 shrinks only to about
the same extent as the ceramics base plates 12. As a result, the
adhesion between the base plates 12 at the peripheral portions of
the base plates 12 which takes place in conventional firing of base
plates is effectively prevented. Furthermore, the surface of the
sheet 11 which may be used in firing base plates according to the
present invention is flat; the construction of an uneven surface or
the formation of pin-holes in the base plates 12 during firing are
effectively prevented.
Two examples of the second embodiment of the present invention are
described below.
According to the first example of the second embodiment of the
present invention, a powder of ceramics 15 of BN having an average
grain size of 10 microns and in an amount of 60% by weight a powder
of carbon 16 having an average grain size of 3 microns and in an
amount of 35% by weight were mixed together with an organic binder
in an amount of 5% by weight. The mixture was than coated on one
surface of a combustible sheet 3 composed of combustible plastics
and then dried to form a coating layer 14. The sheet 11 thus
constructed was placed between the stacked base plates 12 which
were constructed by pressing a powder of glass into the form of a
plate and the supporting base. The base plates 12 were then fired.
Following firing, no scratches could be found on the bottom surface
of the base plate 12 and no adhesion between base plate 12 and the
supporting base occurred.
According to the second example of the second embodiment of the
present invention, a powder of ceramics 15 of a Ni-Zn type ferrite
having an average grain size of 5 microns and in an amount of 80%
by weight and a powder of carbon 16 in an amount of 10% by weight
were mixed together with an organic binder in an amount of 10% by
weight. The mixture was then coated on both surfaces of a
combustible sheet 13 composed of a pulp paper having a thickness of
0.3 mm and then dried to form the coating layers 14. The sheet 11
thus constructed was placed between the stacked base plates 12
which were constructed by pressing a powder of cemented carbide
into the form of a plate and the supporting base. The base plates
12 were then fired. Following firing, no scratches due to thermal
shrinkage could be found on the bottom surface of the base plate
12. Furthermore, undulations in the base plate 12 were decreased to
1/3 or less than those of conventionally fired base plates.
In summary, the second embodiment of the present invention provides
a number of advantages, including the following. First, due to the
shrinkage-inhibiting effect of the powder of carbon 6 and the
lubricating effect of the powder of ceramics 15 and the powder of
carbon 16, adhesion between the plates 12 and the supporting base
during firing and scratching of the base plates due to abrasion
between the base plates 12 and the supporting base during firing
are effectively prevented. Second, due to the constant breadth of
the layer of powder of ceramics 15 remaining between the base
plates 12, undulations and pin-holes in the base plates 12, formed
during firing, are effectively prevented. Third, due to the
construction of the sheet 11 wherein the coating layer 14 of a
constant breadth is coated on the combustible sheet 13, the
construction of the sheet 11 which may used in the firing of
ceramics base plates according to the present invention becomes
easy, resulting in a decrease in costs.
C. THIRD EMBODIMENT
FIG. 3 illustrates a sheet 21 which may be used in firing ceramic
faced base plates according to a third embodiment of the present
invention. The sheet 21 is placed between the ceramic faced base
plates 22 during firing. The sheet 21 comprises a combustible sheet
23, a first coating layer 24 comprising a powder of carbon, which
coating layer 24 is coated on both surfaces of the combustible
sheet 23, and a second coating layer 25 comprising a powder of a
material with a high melting point, which coating layer 25 is
coated on a surface of at least one of the first coating layer
24.
The combustible sheet 23 is preferably constructed of a pulp paper
which may be entirely incinerated when the ceramic faced base
plates 22 are fired. The combustible sheet 23 may be constructed of
a sheet of combustible plastics, such as polyvinyl alcohol. The
first coating layer 24, coated on both surfaces of the combustible
sheet 23, comprises a powder of carbon and a binder therefore and
the thickness of each first coating layer 24 is 15-50 microns. The
first coating layer 24 comprising a powder of carbon functions to
carbonize the combustible sheet 23 during firing and to essentially
prevent shrinkage of the sheet 21 during firing. The second coating
layer 25 comprising a powder of a material with a high melting
point is attached to the surface of the first coating layer 24 with
an adhesive layer 26 of an acrylic resin adhesive or an epoxy resin
adhesive. The material with a high melting point, used in forming
the powder of the second coating layer 25, is selected either from
a ceramics having a high melting point, such as alumina, zirconia,
silicon carbide, silicon nitride, aluminum nitride and boron
nitride, or from a ferrite, such as manganese-zinc and
nickel-zinc.
FIG. 4 illustrates a pre-sheet wherein the first coating layers 24
comprising a powder of carbon are coated on both surfaces of the
combustible sheet 23. Upon receiving an order, the pre-sheet is cut
to a specified size, that is, before the coating of the second
coating layer 25. The adhesive layer 26 is then coated on the
surface of the first coating layer 24 as shown in FIG. 5. The
powder of a material with a high melting point is attached to the
first coating layer 24 via the adhesive layer 26 by means of
electrostatic coating or flow dipping coating. This, the
manufacture of sheet 21 may correspond to the specification of an
order by the election of a material of a high melting point, even
if the order is for a small number and/or for many kinds of sheets.
In addition, since the pre-sheet is cut at the construction stage
of FIG. 5, the instrument used to cut the pre-sheet to the desired
size is not used to cut the material with a high melting point and
so the durability of said instrument is increased.
The ceramic faced base plates 22 are constructed by pressing a
powder of ceramics into the form of a plate. The sheet 21 may be
placed between adjacent ceramics base plates 22 of a green sheet or
ceramics base plates 22, which are stacked in a vertical direction.
The sheet 21 may also be placed between the ceramics base plate 22
and a supporting base. The combustible sheet 23 will be incinerated
during the firing of the ceramics base plates due to the high
temperatures, leaving the powder of ceramics 25 having a high
melting point between the ceramics base plates 22 or between the
ceramic faced base plate 22 and the supporting base. This remaining
powder of ceramics functions to prevent adhesion between the
ceramic-faced base plates 22 and adhesion between the ceramics
faced base plate 22 and the supporting base.
The sheet 21 of the third embodiment of the present invention has
additional advantages. Because the sheet 21 of the third embodiment
of the present invention is constructed by coating the first
coating layers 24 on both surfaces of the combustible sheet 23 and
coating the second coating layer 25 on a surface of at least one of
the first coating layer 24, a constant breadth of each of coating
layers 24 and 25 may be easily obtained and the construction of
sheet 21 is very easy, which results in a decrease in costs. In
particular, since the first coating layers 24 include a powder of
carbon, the combustible sheet 23 is easily carbonized and the sheet
21 shrinks only to substantially the same extent as the ceramics
faced base plates 22. As a result, the adhesion between the
peripheral portions of the ceramic faced base plates 22 which takes
place in conventional firing of ceramic faced base plates is
effectively prevented. Furthermore, since the first coating layers
24 and the second coating layer 25 are each formed separately from
the other, the composition in each of the coating layers 24 and 25
is uniform. In the first and second embodiments of the present
invention, a non-uniform composition of the coating layer may be
obtained when mixing the components of the coating layer, due to
the difference in the specific gravities of the powder of ceramics
and the powder of carbon. Thus, the quality of the coating layers
24 and 25 of the third embodiment of the present invention is
superior in this regard over those of the first and second
embodiments. In addition, since the surface of the sheet 21 which
may be used in firing ceramic faced base plates according to the
present invention is flat, undulations or the formation of
pin-holes in the ceramic faced base plates 22 during firing are
effectively prevented.
An example of the third embodiment of the present invention is
described below.
First coating layers including a powder of carbon were coated on
both surfaces of a combustible sheet 23 composed of a pulp paper
forming two coating layers 24, each of a 30 micron breadth. A
pre-sheet having an 80 micron breadth was obtained. Adhesive layers
26 of acrylic resin were formed on the surface of one coating layer
24. Then, the pre-sheet was cut to a square having the dimensions
of 128 mm by 128 mm. Next, the second coating layer 25 comprising a
powder of alumina having a grain size of 30 microns was adhered to
the surface of the adhesive layer 26 by means of electrostatic
coating. The sheets 21 thus constructed were inserted between eight
adjacent ceramic faced base plates 22 of alumina green sheet
stacked in a vertical direction, each ceramic faced base plate
having dimensions of 128 mm by 128 mm and a thickness of 1.2 mm.
The ceramic faced base plates 22 were then fired. Undulations of
the ceramic faced base plates 22 thus fired were measured and
compared with both those of ceramic faced base plates produced
according to the prior art method wherein a powder of ceramics was
scattered onto the ceramic faced base plates by hand and the first
embodiment of the present invention. TABLE 2 below shows the
results of measurements taken at a span of 80 mm.
TABLE 2
__________________________________________________________________________
Undulations of Ceramics Base Plates Undulations of Ceramics Base
Plates Quality of Max. (microns) Min. (microns) R (microns) -x
(microns) sheet (%)
__________________________________________________________________________
Third Embodiment 25.0 5.0 20.0 15.2 95 First Embodiment 30.6 5.9
24.7 20.2 85 Prior Art 59.7 31.3 28.4 47.0 60
__________________________________________________________________________
In summary, the third embodiment of the present invention provides
a number of advantages, including the following. First, due to the
shrinkage-inhibited effect of the first coating layer 24 comprising
a powder of carbon, adhesion between the peripheral portions of the
ceramic faced baes plates 22 and between the stacked ceramic faced
base plates and the supporting base is prevented. Second, due to
the constant breadth of the layer of powder of ceramics remaining
between the ceramic faced base plates 22, undulations and pin-holes
in the ceramic faced base plates 22, formed during firing, are
effectively prevented. Third, due to the construction of the sheet
21, wherein the first and second coating layers 24 and 25 of a
constant breadth are coated on the combustible sheet 23, the
construction of the sheet 21 which may be used in firing ceramic
faced base plates according to the present invention becomes easy,
resulting in a decrease in costs. Fourth, due to the separate
coating of the first and second coating layers 24 and 25, the
quality of the coating layers is high. Fifth, cutting the pre-sheet
prior to coating the second coating layer 25 on a surface of at
least one of the first coating layers 24 increases the durability
of the instrument used to cut the pre-sheet to the desired
size.
D. FOURTH EMBODIMENT
FIG. 6 illustrates a sheet 31 which may be used in firing ceramic
faced base plates according to a fourth embodiment of the present
invention. According to the fourth embodiment, the sheet 31 is
placed between ceramic faced base plates 32 during firing. The
sheet 31 comprises a combustible sheet 33 and a coating layer 34
coated on at least one surface of the combustible sheet 33. The
coating layer 34 comprises a powder of a material 35 having a high
melting point in an amount of 0.5% to 25% by weight, and a powder
of carbon 36 in an amount of 5% to 90% by weight, a dispersing
agent in amount of 0.1% to 8% by weight, with a binder forming the
remainder of the coating layer.
The combustible sheet 33 is preferably constructed of a pulp paper
which may be entirely incinerated when the ceramic faced base
plates 32 are fired. The combustible sheet 33 may be constructed of
combustible plastics, such as polyvinyl alcohol. The coating layer
34 is coated on the surface of combustible sheet 33 to a breadth
of, for example, 40 microns. A paste comprising the powder of a
material 35 having a high melting point, the powder of carbon 36,
the dispersing agent and the binder is coated on the surface of the
combustible sheet 33 by means of electrostatic coating or flow
dipping coating and then dried to form the coating layer 34. The
powder of material 35 with a high melting point has an average
grain size of 30-40 microns. The powder of a material 35 is
selected either from a ceramics having a high melting point, such
as alumina, zirconia, silicon carbide, silicon nitride, aluminum
nitride, and boron nitride or a ferrite, such as manganese-zinc and
nickel-zinc. The grain size of the powder of carbon 36 is about 0.6
microns. The dispersing agent comprises a surface-active agent. The
surface active agent is a fluoric agent, a nonionic agent or an
anionic agent. Due to the provision of the dispersing agent, the
powder of material 35 with a high melting point may be uniformly
dispersed in the coating layer 34 resulting in the provision of an
almost unform composition of said layer, which prevents cracking in
the coating layer 34 at the time of cutting the sheet 31. The
binder comprises a plastic binder, such as an acrylic resin binder
and an epoxy resin binder. An explanation regarding the limitations
to the above values is provided below.
A powder of material 35 with a high melting point functions to
prevent adhesion between the ceramic faced base plates 32 during
firing. If the powder of material 35 with a high melting point is
included in an amount less than 0 5% by weight in the coating layer
34, the adhesion-preventing effect of the powder of material 35 is
no longer satisfactory. If the coating layer 34 comprises the
powder of material 35 with a high melting point in an amount
greater than 25% by weight, uneveness in the surface of the coating
layer 34 increases and the ratio of the powder of carbon 36 to the
powder of material 35 in the coating layer 34 decreases, which
results in decreasing the effects of the powder of carbon 36
described below.
The powder of carbon 36 functions to carbonize the combustible
sheet 33 during firing and to inhibit shrinkage of the sheet 31 to
such an extent that the shrinkage rate of the sheet 31 is
substantially the same as that of ceramic faced base plates 32. If
the coating layer 34 comprises the powder of carbon 36 in an amount
less than 5% by weight, the shrinkage-inhibiting effect of the
powder of carbon 36 is no longer satisfactory. If the coating layer
34 comprises the powder of carbon 36 in an amount greater than 90%
by weight, a uniform dispersion of the powder of material 35 with a
high melting point in the coating layer 34 is difficult to
obtain.
The dispersing agent functions to uniformly disperse the powder of
material 35 with a high melting point and the powder of carbon 36
in the coating layer 34. If the coating layer 34 comprises the
dispersing agent in an amount less than 0.1% by weight, its
dispersing effect is unsatisfactory. If the coating layer 34
comprises the dispersing agent in an amount greater than 8% by
weight, the dispersing agent has an undesirable effect on the
ceramic faced base plates 32.
The sheet 31 thus constructed is placed between adjacent ceramic
faced base plates 32 which are stacked in a vertical direction or
between the ceramic faced base plate 32 and a supporting base used
to support the stacked ceramic faced base plates 32 during firing.
The combustible sheet 33 will be incinerated during firing, leaving
the powder of material 35 with a high melting point. This remaining
powder of material 35 with a high melting point functions to
prevent adhesion between the ceramic faced base plates 32 and the
supporting base. The powder of carbon 36 inhibits shrinkage of the
sheet 1 during firing and prevents adhesion between the peripheral
portions of the ceramic faced base plates 32 and between the
ceramic faced base plates 32 and the supporting base. The coating
of the coating layer 34 on the surface of the combustible sheet 33
assures a constant breadth of the layer of powder of material 35
remaining during firing and a high quality of the fired ceramic
faced base plates 32 having minor undulations and few pin-holes,
and further enables the easy construction of easy construction of
sheets 31.
The fourth embodiment of the present invention has additional
advantages. Due to the dispersing agent, the powder of material 35
is uniformly dispersed in the coating layer 34, which results in
effective prevention of cracking in the coating layer 34 and easy
cutting of the sheet 31 without severely decreasing the durability
of the instrument used to cut the sheet 31. In addition, only a
small amount of the powder of material 35 with a high melting point
remains on the surface of ceramic faced base plates 32 following
firing and so the removal of the remaining powder is easy.
Examples of the fourth embodiment of the present invention are
described below.
Coating layers 34 having the compositions shown in TABLE 3 were
coated by means of impregation coating on both surfaces of a
combustible sheet 33 composed of pulp paper having a 40 micron
thickness. The coating layers thus forming, each of a 40 micron
thickness, were then dried. The sheets 31 thus constructed were
inserted between eight adjacent ceramic faced base plates 32 of
alumina green sheets stacked in a vertical direction, each ceramic
faced base plate 32 having a thickness of 1.2 mm. Undulations of
the fired ceramic faced base plates 32 were measured after firing
and were compared with those of a comparison example having the
compositions shown in TABLE 3. The comparison example corresponds
to the first embodiment of the present invention. TABLE 3 below
shows the results of measurements of undulations taken at the span
of 80 mm.
TABLE 3 ______________________________________ Undulation of
Ceramics Base Plates COMPOSITIONS Example 1 Example 2 Example 3
Example 4 Comparison ______________________________________ Powder
of material 35 having a high melting point Alumina Alumina Alumina
SiC Alumina of 35 of 35 of 35 15% 55% micron micron micron size 10%
size 3% size 20% Powder of carbon 36 of 0.6 micron size 62.5% 70%
30% 50% 35% Dispersing Agent Fluoric Fluoric Nonionic Nonionic None
surface- surface- surface- surface- active active active active
agent 1.5% agent 3.0% agent 4.5% agent 6% Binder Acryl Acryl Epoxy
Epoxy Acryl resin resin resin resin resin 26% 24% 45.5% 29% 10%
Undulations Maximum: micron 28.0 25.0 29.0 26.3 30.6 Minimum:
micron 5.5 4.8 5.0 6.0 5.9 R: micron 22.5 20.2 24.0 20.3 24.7 -x:
micron 17.8 18.3 17.0 18.7 20.2
______________________________________
In summary, the fourth embodiment of the present invention provides
a number of advantages including the following. First, due to the
shrinkage-inhibiting effect of the powder of carbon 36, adhesion
between the ceramic faced base plates 32 which takes place in
conventional firing is prevented. Second, due to the constant
breadth of the layer of powder of material 36 with a high melting
point remaining between the ceramic faced base plates 32,
undulations and pin-holes in the ceramic faced base plates 32,
formed during firing, are effectively prevented. Third, due to the
construction of the sheet 31 wherein the coating layer 34 of a
constant breadth is coated on the combustible sheet 33, the
construction of the sheet 31 is easy, resulting in a decrease in
costs. Fourth, due to the dispersing agent, the coating layer 34 is
uniform in composition and cracking in the coating layer 34 at the
time of cutting the sheet 31 is prevented, increasing the
durability of the instrument used to cut the sheet 31.
Although only four preferred embodiments of the present invention
have been described in detail, it will be appreciated by those
skilled in the art that various modifications and alterations can
be made to the particular embodiments shown without materially
departing from the novel teachings and advantages of the invention.
Accordingly, it is to be understood that all such modifications and
alterations are included within the scope of the invention as
defined by the following claims.
* * * * *